EP0350447B1 - Warp tension control process and loom with a warp-tensioning device - Google Patents

Description

• zyklische Einflüsse infolge Fachwechsel und Blattanschlag, abhängig von Webzyklen, Bindungs- und Musterungsrapport
• sporadische Einflüsse wie Relaxationseffekte bei Stillstand und Anlauf der Webmaschine sowie
• kontinuierliche Einflüsse z.B. mit dem Ablauf des Kettbaums.

The invention relates to a method for warp tension control in weaving machines and a weaving machine with warp tensioning elements for carrying out the method. The central importance of warp tension in weaving is discussed, for example, by S. Schlichter: "The influence of the individual machine elements on the movement and force profiles in warp and weft on high-performance weaving machines", dissertation, Aachen, 1987, discussed in detail. A "good" temporal warp tension curve is a prerequisite for obtaining usable fabrics. On the one hand, the warp tension must be large enough to produce firm bonds when the sheet is attached and to prevent loose threads from becoming jammed at any time. On the other hand, yarn-specific maximum values must not be exceeded at any time and at any place in order to avoid warp thread breaks. Fabric and weave quality as well as efficiency and possible weaving machine speed largely depend on the warp tension curve. Different influences determine the warp tension curve:

• cyclical influences due to a change of subject and page stop, depending on weaving cycles, weave and pattern repeat
• sporadic influences such as relaxation effects when the weaving machine is at a standstill and when it starts
• continuous influences, for example with the running of the warp beam.

To secure the necessary warp tension curve, passive, spring-loaded tensioning boom systems have previously been used, in some cases also tensioning rollers mechanically firmly coupled to the main loom drive, as disclosed, for example, in US-A-34 83 897 (CH-A-472 521).

In order to be able to at least partially meet the increasing requirements for high-speed weaving machines, various improvements have been proposed. For example, a low-dimensional spanning tree system according to EP-A-0 109 472 in order to reduce harmful phase shifts, or in DE-A-35 32 798 a control device for the warp thread tension by shifting the position of a match tree in order to be able to avoid contact points. The latter is also intended with controlled warp let-off devices (example EP-A-0 136 389). However, all these known proposals can only result in improvements in partial aspects and to a very limited extent.

The object of the present invention is therefore to overcome the known problems in connection with the warp tensions and to achieve the best possible warp tension curves under all conditions and in any fabric pattern. In particular, higher weaving machine speeds and performances, higher fabric quality and benefits, fewer production interruptions due to thread breaks and stapling and expanded fabric patterning options are to be achieved.

In terms of the method, this task is solved in the operation of a weaving machine in that the warp tension is modulated by at least one separate drive via warp tensioning elements and is thereby controlled individually and individually. As a result, the warp tension can be optimally adapted to all desired conditions in the course of each cycle.

The separate drive can advantageously be controlled by a sequence of pulses which are freely programmable in terms of amplitude, pulse width, zero position and phase position and which are matched to the weaving machine cycles and the operating mode of the weaving machine.

By controlling the pulses with a pulse duration that is shorter than a weaving machine cycle, the warp tension can also be influenced only in a desired partial area of a cycle. The warp tension can be optimized in a targeted manner in the individual sub-areas by controlling a pulse in several sub-areas of a weaving cycle or a weft repeat. The pulses can be controlled independently.

By compensating pulses in the sub-areas of the weaving machine cycles in which maximum values of the warp tension occur, these maximum values can be reduced, for example below a setpoint set according to the yarn strength. As a main cause of production interruptions, warp thread breaks can be largely avoided and the efficiency can be increased accordingly. In an analogous manner, minimum values can also be increased in some areas, so that the warp tension does not drop below an adjustable setpoint, below which, for example, the warp threads tend to jam too much.

When operating a terry weaving machine with pile forming elements, in addition to the warp tension modulation, at least one pile forming element can also be actuated by a separate drive and can be controlled individually and individually. This enables an improvement in terry weaving and pile quality.

A weaving machine for carrying out the method is characterized by at least one servo motor as a separate drive, which is coupled via a reduction gear and / or transmission elements to at least one warp tension member influencing the warp tension, and where the servo motor is connected to a control and regulation circuit with a control input and can be controlled individually in individual shots. Preferably, the servo motor can be electronically commutated and brushless and have a low inertia rotor with permanent magnets of high field strength. This design results in a particularly highly dynamic drive, with high peak and continuous outputs with relatively low thermal losses to be managed. As a result, the method according to the invention can be carried out with particularly high precision and at high speeds and weaving capacities.

Further advantageous designs, as described in the subclaims, can have servomotors with rare earth magnets and in particular with magnets made of Nd-Fe-B connections. Their particularly high field strengths, both in absolute terms and in relation to their weight, lead to particularly high engine outputs and weaving machine speeds. A further increase in performance can be achieved in a simple manner by cooling the servomotor stator.

The weaving machine according to the invention can have any controlled warp tensioning elements. The warp tension member can e.g. an additional tension roller, which is only driven by the associated servo motor. Or, the warp tensioning element can also be an existing spanning tree system that is driven in a basic movement by the main loom motor and where this basic movement is only additionally modulated and controlled by the servomotor. This means that the constant basic movement can provide constant compensation, while the servo modulation can handle all changing conditions, e.g. optimized according to the pattern. The warp tensioning element can also be driven symmetrically on both side cheeks of the weaving machine by a servo motor, preferably both servo motors being driven and controlled synchronously by only one motor controller. This results in absolutely symmetrical fabrics even with large weaving widths.

A reduction gear with a primary element of low inertia on the motor shaft allows the high dynamics of the servo motor to be transmitted down to the chain tensioning element.

A plurality of control inputs, measuring inputs and / or data outputs of the control and regulation circuit as well as an assigned computer unit can be provided, bidirectional communication with the weaving machine being possible. This results in an even more universal control and regulation of the warp tension curve and, at the same time, operating data for further processing and for optimizing fabric quality, machine performance and efficiency can be prepared and delivered.

In looms with at least two warp thread sets, each warp thread set can be assigned a warp tension member with an associated servo motor, which can be controlled independently of one another. The warp tension curve of each warp thread group can thus be individually optimized.

In principle, several warp tension elements can be controlled with one or two servo motors each independently of the same control and regulation circuit and thus each warp tension element can be optimally adjusted independently to the desired weaving result.

In the case of a terry weaving machine, in addition to the warp tensioning element and its servo drive, at least one pile formation element with an associated further servo motor can be provided, the control of this servo motor being matched to the terry movement. This can also influence and optimize pile formation.

The invention is explained in more detail below on the basis of exemplary embodiments in conjunction with the drawings.

• Fig. 1 eine erfindungsgemässe Webmaschine mit Kettspannungssteuerung;
• Fig. 2 ein Kettspannungsorgan mit Spindelstange, Servomotor und Untersetzungsgetriebe;
• Fig. 3a,b,c,d verschiedene Anordnungen von Kettspannungsorganen;
• Fig. 4 ein Schaltschema einer erfindungsgemässen Webmaschine mit einer Steuerungs- und Regelungsschaltung;
• Fig. 5 eine servobetriebene, massearme Kettspannwalze;
• Fig. 6a,b,c,d,e Beispiele von Kettspannungsverläufen und gesteuerten Kettspannungspulsen;
• Fig. 7 eine Frottierwebmaschine mit zwei Kettbäumen und Servosteuerung;
• Fig. 8 ein Beispiel einer Kettspannungssteuerung mit konstanter Grundbewegung und Servomodulation.

It shows:

• 1 shows a weaving machine according to the invention with warp tension control;
• 2 shows a chain tensioning element with a spindle rod, servo motor and reduction gear;
• 3a, b, c, d different arrangements of warp tension members;
• 4 shows a circuit diagram of a weaving machine according to the invention with a control and regulating circuit;
• 5 shows a servo-operated, low-mass warp tensioning roller;
• 6a, b, c, d, e examples of warp tension profiles and controlled warp tension pulses;
• 7 shows a terry weaving machine with two warp beams and servo control;
• 8 shows an example of a warp tension control with constant basic movement and servo modulation.

1 schematically shows a weaving machine according to the invention with a warp tension control. The chain 7 runs from a warp beam 1 via a tensioning beam 4 to the shed 9 with shafts 14 and reed 12. The fabric 10 is drawn off onto a fabric beam 3 via a breast beam 6 and a take-off roller 18. The warp tensioning device 20 consists of a roller 21 as a warp tensioning member, a rack 24 as a transmission element, a reduction stage 63, a pinion 62 on the shaft of a servo motor 36 and a control and regulating circuit 88 move up and down at any rhythm. This movement results in an extension or shortening of the chain 7 and thus a change in the chain tension determined by the shrimp elasticity. Appropriate timing of the servo motor can in principle generate any desired change in warp length or any desired warp tension curve. With a Warp tension sensor 52, which is connected to the control and regulation circuit 88, the resulting warp tension is continuously monitored and included in the optimal warp tension control.

In particular, the warp length control caused by the change of subject can be partially or completely compensated for by the warp tension control 20. In addition to existing spanning tree systems 4, the warp tensioning device 20 now creates a possibility of influencing the warp tension whenever the known spanning tree systems are increasingly unable to guarantee a reasonably optimal warp tension curve with increasing speeds. The warp tension control can also be integrated in the tensioning boom system 4 itself or replace it (e.g. as in Fig. 7).

Fig. 2 shows a warp tension control with a radially mounted spindle rod 27, which also moves the warp tension member 21 linearly up and down. For this purpose, the spur gear 63 has an internal toothing running on the spindle thread 28. The spur gear 63 is axially supported to support the warp forces.

The servo motor 36 has a cooling device 61, in which case a fan supplies cooling air along the stator housing of the servo motor provided with cooling ribs.

The servomotor has a low inertia rotor with permanent magnets of high field strength, ie high remanence and high demagnetization field strength. The low inertia of the rotor enables high dynamics, and high field strengths result in high motor torques and outputs, which together result in a high weaving machine speed. Advantageous magnetic materials are rare earth magnets such as SmCo compounds and especially Nd-Fe-B compounds. The use of permanent magnets on the rotor of the servo motor creates ohmic losses only on the stator and not on the rotor of the motor. The resulting heat loss can be dissipated easily and to a greater extent here, for example by means of air or water cooling of the stator. This enables a further increase in the performance of the servo motor also with regard to overload peaks, especially when using neodymium magnets.

Like the rotor of the servo motor, reduction gears and transmission elements are designed for the lowest possible inertia losses. For this purpose, a two-stage reduction gear with a light spur gear pinion 62 is used on the axis of the servo motor in FIG. 2, which, as the primary element with low mass inertia, rapidly reduces the motor speed, e.g. by a factor of 3 to 5. Overall, the engine power share required to accelerate the moving parts, from the motor rotor to the reduction gear, transmission element to the warp tensioning elements, is kept as low as possible, thereby enabling the very high weaving machine speeds that are sought.

3 shows various arrangements of warp tension members 21, 22, 23 with lower (16) and upper (17) guide rollers, the warp tension members being moved in a translatory (25) or rotary (26) manner. The arrangement of FIG. 3a acts, as in FIG. 1, symmetrically with respect to the shed 9. All the warp threads, that is to say high and low shed coulters, are influenced to the same extent. In Fig. 3b the subjects are controlled asymmetrically. If, depending on the binding, individual shafts remain in the high shed during a sheet stop, their warp thread sets can then be relative by the warp tensioning element (in position 22a) are relaxed, while the remaining warp threads 7g at the same time receive a necessary minimum tension by the tension roller 4. For optimal tension control of all warp threads 7h and 7g, the tensioning roller 4 can also be servo-controlled (direction of movement 26). Positions of the warp tension member between 22b and 22c, on the other hand, result in an essentially symmetrical warp force control in the high compartment 7h and in the deep compartment 7t. 3c, the warp threads are divided into two groups 40, 41 by two warp tensioning members 21, 22. This means that each warp thread group can be optimally controlled individually and independently of the other by the associated warp tension element and its servo motor. The same effect can also be achieved with the walk-like chain tensioning element 23 in FIG. 3d. For this purpose, the organ 23 is moved translationally in the direction 25 by a first servo motor. A second servo motor rotates the member 23 about its axis of rotation 29 in the direction 26.

4 shows a circuit diagram of a weaving machine according to the invention. A control and regulation circuit 88 with a control input 89 consists of a terry control 74 which controls a motor controller 76. The motor controller 76 drives the servomotor 36 via a power unit 77 connected to a supply 73. The motor controller 76 is connected to a motor angle sensor 79 for the purpose of synchronization. With the warp tension control 74, a plurality of servomotors 36, 37 for actuating a plurality of warp tension members can also be controlled independently (76, 77, 79 each a and b). Control of the deflection (and thus the warp tension) can thus be achieved in very small steps of, for example, only 0.1 mm. The warp tension control 74 is connected to the weaving machine bus 82 and to a weaving machine crank angle sensor 81 for absolute synchronization of the motor control with the weaving machine, for forward and backward running. On the The weaving machine bus 82 is further coordinated with the warp let 84, the dobby machine control 86 and the other weaving machine functions such as fabric take-off and color changer control. A display and operating unit 87 as well as various measurement inputs 83 (for example from warp tension sensors) and data outputs 90 are also connected to the weaving machine bus 82. This enables bidirectional communication between the weaver and the warp tension control, as well as a link to a central control system.

The control control circuit 88 also includes a computer unit with memory. A corresponding single-shot optimization of the warp tension curve can thus be generated, saved and called up again for any fabric patterns generated by the shaft control. A warp tension modulation is assigned to each shot of a pattern repeat.

By using a warp tension sensor 52 (FIG. 1), which is connected to the control and regulating circuit 88, a desired predetermined optimal warp tension curve can be automatically maintained.

FIG. 5 shows a low-mass tensioning roller system 66, which executes a rotary movement as a chain tensioning element (same as the tensioning tree 4 in FIG. 3b). The tensioning roller system is driven by a servo motor 37 via a pinion 62, an intermediate stage 63 and a toothed segment 64. It consists of a rigid support roller 67, a light pendulum tube 69 and connecting supports 68. This results in a low mass inertia of the tensioning roller system 66. An additional, adjustable biasing spring 71 and a damper 72, acting on the tensioning roller 66, can also be provided. The servo motor 37 is also controlled by the warp tension control 74 (Fig. 4) driven, but it has its own motor control (76b, 77b, 79b). In the case of a terry weaving machine, such a low-mass tensioning tree system can also be used as a pile tensioning tree or pile pendulum roller.

The pile pendulum roller has the task of delivering the pile chain accordingly quickly and with the least possible tension during the almost sudden pushing open of the pile at full stop (this is especially the case with control of the web shop). To do this, the pile pendulum roller must move very quickly, without delay and easily. On the other hand, however, a minimal pile warp tension must be maintained during the rest of the time in order to ensure undisturbed warp feed without thread crossings. With previous suspended pendulum roller systems, these conflicting requirements can only be met to a very limited extent (FIG. 6e). 5, these contradicting requirements can now be met and optimal warp tension profiles can be controlled for any operating modes and terry rhythms.

• Kettspannungsverläufe mit bisherigen Spannbaumsystemen 103, 106 bis 108, 111 bis 114, 124,
• auf modulierte, servogesteuerte Kettspannungspulse 100, 104, 109, 116 und
• resultierende servogesteuerte Kettspannungsverläufe 105, 110, 121 bis 123, 125.

The warp tension control according to the invention is explained in examples with reference to FIGS. 6a to d. The courses of warp tension F over several weaving cycles Z and weave repeats are shown as a function of time:

• Warp tension curves with previous spanning tree systems 103, 106 to 108, 111 to 114, 124,
• to modulated, servo-controlled warp tension pulses 100, 104, 109, 116 and
• resulting servo-controlled warp tension curves 105, 110, 121 to 123, 125.

6a shows an optimal servo-controlled warp tension pulse curve 100 to compensate for a corresponding warp length change when the compartment is opened. The optimal curve 100 is controlled by the servo motor such that its amplitude A, pulse width B, zero position U, pulse duration P and phase I correspond to the target compensation in the weaving machine cycle. By contrast, a previously sprung tensioning tree system, especially at high weaving machine speeds, only achieves poor, "smeared" compensation in accordance with curve 101. As a result of inertia, there is a phase shift dI and a reduced amplitude. The previous compensation by the spanning tree thus deviates from the optimal course 100 by the areas 102 and 120. At the same time, warp tension increased by area 102 occurs when the sluggish tensioning roller is unable to follow the specialist movement. The tensioning roller then overshoots with an undesirable relaxation of the warp threads corresponding to the region 120.

6b, the previous warp tension curve 103 is modulated by several servo pulses P1, P2, P3 so that an optimized warp tension curve 105 is created. The course 105 is regulated by the pulses P1, P2 under a predetermined maximum target value Fmax corresponding to the yarn strength. On the other hand, pulse 3 does not fall below a predetermined minimum warp tension Fmin.

The previous average warp tension curve 106 of a warp thread family in FIG. 6c shows an example in which this warp thread family remains in the high shed in cycle 1 when the sheet is stopped and therefore has high tension values. In the subsequent cycle 2, the compartment closes again and the warp tension values remain low. It should be noted that the tension of individual warp threads is higher than the maximum Values 107 and lower minimum values 108 reach than the average warp tension values 106. Individual threads can therefore tear and cling earlier than would be expected due to the average tension curve 106. This must be taken into account when specifying the setpoints Fmax and Fmin. Correspondingly, the pulses P4, P5, P6 of the servo modulation 109 are activated in order to achieve a desired resulting warp tension curve 110. It should also be noted that very short warp tensions (Fmaxk) are permissible for a very short time, e.g. as tension peak 126 at the blade stop, than with longer exposure times, e.g. in the open compartment, which is compensated here by pulse P4.

6d shows a change of weave from a 2: 1 warp twill weave to a 1: 1 plain weave. So first a weft repeat 3, where alternately a warp thread sheet always remains in the high compartment when the sheet stops and where the other two thread sheets close or change at the same time. In cycle 1, therefore, the warp tension curve 111 of the first set of threads (in the high compartment) shows high values, while the tensions of the second and third set of threads 112 and 113 remain low. The tension curve 112 is high in cycle 2 and 113 high in cycle 3. The servo pulses 116 in the unloading direction are always applied to the respective group of threads in the high compartment, for example by arranging the warp tension members according to FIG. 3b. The resulting warp tensions 121, 122, 123 then all remain below Fmax. Then the change to a two-shot repeat with two sets of threads, which always close when the blade stops (each shaft changes after each shot), the average warp tension curve of all warp threads is below Fmax. The servo modulation 116 is changed accordingly in cycles 4 and 5. This could be followed by a 2: 1 and a 1: 1 binding again. This would give a fabric pattern repeat N of five cycles.

6e shows the servo-optimized course of a pile warp tension 125 with a 3-shot terry rhythm. For this purpose, a pile pendulum roller according to FIG. 5 is controlled by the servo motor in such a way that the pile warp tension is momentarily reduced to an almost arbitrarily small value F1 of a few grams by means of a corresponding pulse during the pole shift 91. Between the pile-open phases 91, the tension is brought to a higher, substantially constant value F2, which can be optimally adapted to the yarn and the operating parameters. While curve 125 generated according to the invention has an optimal warp force curve, this is not possible with previous pendulum rollers, according to curve 124. The minimum warping force F1 and the optimum phase position and pulse shape with respect to pole extension 91 cannot be achieved there.

FIG. 7 shows a terry weaving machine with fabric control, in which the fabric control elements, here a tensioning tree 4 and a breast tree 6 as pile formation elements, are controlled by servomotors 36, 37. The basic warp beam 1 is arranged at the top and the pile warp beam 2 is arranged at the bottom for easy interchangeability. In the fabric control, the looping is carried out by periodic horizontal movements of the fabric by means of the breast beam 6 and spreader 128, whereby the fabric edge around the fabric stroke is pulled away from the reed attachment point. The reed movement remains unchanged. The resulting pile height is essentially proportional to the tissue stroke. When the full stop is reached, the base chain 7 is pulled back to the sheet attachment point by the breast beam with a spreader and tension roller 4, while at the same time the pile chain 8 must not be pulled back by the light pile tensioning beam 117. Subsequently, until the next partial stop, base chain 7 and pile chain 8 have to be rapidly advanced together by the fabric stroke corresponding to a desired pile height.

For this purpose, the two tensioning trees 4 and 117 have to release the corresponding chains 7 and 8 just as quickly and at the same time ensure the necessary chain tension values. This rapid warp feed by a precisely defined fabric stroke of e.g. 20 mm takes place in less than one weaving cycle T. This results in conflicting requirements for both warp tensions in the different sub-areas of the cycles or repeats (fabric feed after full stop, fabric retraction before full stop and normal warp let-off speed in between) in order to achieve optimal weaving properties and through appropriate warp tension pulses To achieve tissue qualities.

These conflicting requirements for the basic and pile chain tensions can only be met very inadequately here with the previous spring-loaded spanning tree systems. 7 can largely meet these requirements. For this purpose, the terry toweling elements 4 and 6 are driven separately by a servomotor each. The breast beam 6 is driven by the servo motor 36 via a lever 131 with an axis of rotation 132 and teeth 136, while the tensioning roller 4 is operated by a separately controlled servo motor 37 via a lever 140. The warping forces 137 and 138 are preferably absorbed here by pretensioning springs 141 and 142, which act on the levers 131, 140. The springs 141 and 142 are set in such a way that average warp force values at an average fabric stroke are just compensated by their spring forces. When the tensioning roller 4 is actuated, the specialist compensation is also integrated here. The breast beam 6 or the tensioning beam 4 can be driven laterally or in the middle on one side via the levers 131, 140. As a result of the central drive, asymmetrical twists, which can cause asymmetrical fabric and pile formation, can be avoided. A An advantageous, even more powerful design can also have two servo motors 38a, 38b, which are each arranged on a side cheek 134a, b of the weaving machine and synchronously drive the breast boom 6 and the tensioning roller 4 via a lever. Then both servomotors 38a, b can be operated by only one motor controller 76 and one power unit 77. In addition, the pile tensioning tree 117 as a secondary pile-forming member, as described in FIG. 5, can also be controlled by the tissue or terry control 74 by means of a further independent servo motor.

The inventive servo control of the warp tensions can also be applied to a weaving machine with an effect tree instead of the pile warp beam 2 of the terry weaving machine from FIG. 7.

Fig. 8 shows an example with a warp tension member which is driven by the loom main motor in a constant basic movement, this basic movement being freely modulated by a servo motor. A spanning tree 4 is rotatably mounted on a one-armed lever 144. The lever 144 is articulated to a two-armed lever 146, the other end of which has a toothing 32. The central pivot bearing 147 is held stationary in the weaving machine frame. The servomotor 36 moves, via a worm pinion 33 and the toothing 32, the lever 146 and the lever 144, the tensioning roller 4. The lower end of lever 144 is connected to the weaving machine main motor shaft 13 via a coupling rod 148 and an eccentric 149. As a result, the spanning tree 4 is forcibly driven in a fixed, cyclical basic movement 150. This can roughly correspond to a constant specialist adjustment. The actual optimization of the warp tension and its adaptation to the change of binding then takes place by means of the single-shot free modulation from the servomotor 36 to the upper end of lever 144.

The method according to the invention and the corresponding weaving machines effectively open up a new degree of freedom for weaving that previous weaving machines do not have:

The arbitrary, free modulation of the warp tension curves and thus correspondingly extended pattern options. As explained, this can also be automated.

Claims (18)

1. A method of controlling torque tension in looms, characterised in that the warp tension is modulated by at least one separate drive by way of warp-tensioning elements and ls triggered on an individual pick basis and freely.

2. A method according to claim 1, characterised in that the separate drive is triggered by a sequence of pulses which are freely programmable in amplitude, pulse width, zero position and phase position and which are adapted to the loom cycles and the nature of operation of the loom.

3. A method according to claim 2, characterised in that pulses are triggered with a duration P shorter than a loom cycle T.

4. A method according to claim 2, characterised in that a pulse is triggered in each of a number of partial zones of a pick repeat, such pulses being independent of one another.

5. A method according to claim 2, characterised in that in those partial zones of the loom cycles in which warp tension peaks occur, pulses reducing such peaks, for example, below an adjustable set value, are triggered.

6. A method according to claim 1 of operating a terry loom having pile-forming elements, characterised in that in addition to the warp tension modulation at least one pile-forming element is actuated by a further separate drive and is triggered on the basis of individual picks and freely.

7. A loom for the practice of the method according to claim 1, characterised by at least one servomotor (36 - 38) as separate drive, the servomotor being connected by way of a reduction transmission (62 - 64) and/or transmission elements (24, 27, 131) to at least one warp-tensioning element (21, 22) affecting warp tension, the servomotor being connected by way of a control input (89) to an actuating and control circuit arrangement (88) and being triggerable on an individual pick basis and freely.

8. A loom according to claim 7, characterised by an electronically commuted brushless servomotor having a rotor of low mass inertia and high-field-strength permanent magnets.

9. A loom according to claim 8, characterised in that the servomotor (36 - 38) has rare earth magnets.

10. A loom according to claim 8, characterised in that the magnets consist of Nd-Fe-B compounds.

11. A loom according to claim 8, characterised in that the servomotor has a cooled stator (61).

12. A loom according to claim 7, characterised in that the warp-tensioning element (66) is coupled for direct drive only with the servomotor.

13. A loom according to claim 7, characterised in that the warp-tensioning element is drivable in a basic movement by the main motor of the loom, such basic movement being additionally modulatable or controllable by the servomotor.

14. A loom according to claim 7, characterised in that a reduction transmission having a primary element (33, 62) of low mass inertia is provided, such element being connected to the motor shaft.

15. A loom according to claim 7, characterised in that a number of control inputs (87, 89), measuring inputs (83, 85) and/or data outputs (90) of the control and regulation circuit and an associated computer unit are provided, two-way communication with the loom being possible.

16. A loom according to claim 7 having at least two warp yarn sheets, characterised in that a warp-tensioning element with an associated servomotor is associated with each warp yarn sheet, the sheets being triggerable independently.

17. A loom according to claim 7, characterised in that the warp-tensioning element is drivable symmetrically on both side uprights (134a, 134b) of the loom by a respective servomotor (38a, 38b), both the servomotors preferably being driven and controlled synchronously and together by a single motor control (76).

18. A terry loom according to claim 7, characterised in that in addition to the warp-tensioning element and its servo drive at least one pile-forming element (6, 128) with an associated further servomotor is provided, the triggering of the latter servomotor being adapted to pile formation.

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